Method of lowering the tendency towards setting of potassium nitrate and potassium nitrate of free-flowing form with a reduced tendency to setting



Patented Nov. 4, 1952 UNITED ST TE S METHOD OF LOWERING THE TENDENGYTOWARDS SETTING OF POTASSIUM NI- TRATE AND POTASSIUM NITRATE 'OFFREE-FLOWING FORM WITH A REDUCED TENDENCY TO SETTING AlexanderButch'art, North ore eentararus'sam Scotland, assig'nor to ImperialChemical Industries Limited, a corporation of Great Britain No Drawing.Application April -1, -1 949,'Seria1No. 85,024. In Great BritainDecember 29, --1948 '8 Claims. (ores- 162') l The present invention isconcerned with a method of lowering the tendency towards setting ofpotassium nitrate and. with providing potassium nitrate of free-flowingform with a reduced tendency to setting, which is partic- I be appliedto finely divided potassium nitrate produced by a crystallisationprocess capable of passing through e. g. a 30, 60 or 100 mesh sieve(BSS). Naturally coarsely crystalline free-flowing potassiumnitrate,ascrysta1lised in commercial manufacturing processes, forexample, potassium nitrate capable of passing through a mesh sieve andretained by a 30 mesh sieve, can also beneficially be treated accordingto the invention, this coarsely crystalline salt, however, is less proneto setting than 'finely divided potassium nitrate.

This application is related to application Serial 'No. 85,728, filedApril '5, 1949, to Butchart and Whetstone. That application'disclosesand claims the formation of a free flowing ammonium sulphate by theaddition thereto of small amounts of sulphonated aromatic dyestufi whichis soluble in a saturated aqueous solution of ammonium sulphate andwhich in such'solution conditions it'to produce on-c'rystallizationammonium sulphate in the form of thin fragile crystals whichare friableowing to their facial development relative to the -cleav'ageplanes.

According to the present invention the method of lowering the tendencytowards setting of potassium nitrate comprises treating'thc potassiumnitrate with a dyestufi of sulphonated aromatic character which insolution in a saturated aqueous solution of potassium nitrate conditionssaid potassium nitrate solution to produce on crystallization potassiumnitrate in the form of thin and fragile crystals, possessing [001]crystal "habit and being thereby friable owing to their facialdevelopment relative to the 'cleavageplanes of the crystals. I

According to the present "inventio potassium nitrate which is innon-coherin'g and free-flowing form contains'a dy'es'tufi of sulphonatedaromaticcliaracte'r which in solution in 'a-saturated aqueous solutionof i-potassium nitrate conditions said "potassium nitrate solution toproduce on crystallisation potassium nitrate 'inthe form of thinfr'ag'ile crystals, friable owing to their facial development relativeto the cleavage planes.

The phrase dyestufi of sulphonate'd aromatic character includes soluble-salts of an aromatic dyestuff having at least one =sulphonic acid."group and "aromatic dyestufis having at least one sulphonic acid=sub'stituent :group .per dye 11101801118.

Particularly suitable dyestuffs "which most markedly lower the tendencytowards setting of potassium nitrate are:

1:4 dia'mino anthraquinone '2-sodium sulphonate.

1:415:21 t'etra'mino anthraqui-none 'disulphonic acid (sodium salt).

Examples of dyestuffs of sulphonated aro- 'Iriatic character which aresoluble in saturated potassium nitrate solution but which in lesserdegree than the above reduce "the setting tendency of potassium nitrateare:

Edicol Amaranth (Colour Index No. 184

Dyes comprising 3 naphthol 6-sulphonic acid. or fi naphthol3:6-disulphonic acid coupled with dia'z'oti'zed 's'ul'phoriated "aniline'or 'toluidine.

Azofuchsin'e G (comu'ri'ndex No. 153) Fast Red E (Colour index-No. 182)Chlorazol Sky Blue (Colour Index lfio. 518) Acid Green M (Colour Indeir180.669) V Tartrazine (Colour Index 'No. 640) The following dyestuffsexemplify those soluble in water, and-at leastslig'htly soluble '-in"saturated potassium nitrate solutions but which even so have onl'yaaslight tendency "to reduce the setting and also to maintain thefree-flow- 'ing nature of potassium i'iitratez AeidMa'g'en'ta (ColourInde'xNo. B92) C rmoisine-fins (Colour Index No.29)

3 Carmoisine LS (Colour Index No. 180) Bismarck Brown (Colour Index No.331) Hydrazine Yellow SO (Colour Index No. 637) Acid Green G (ColourIndex No. 666) Erioglaucine Extra (Colour Index No. 671) Acid Violet4BNS (Colour Index No. 698) 1:5 diamino anthraquinone 2-sulphonic acid.

It has been found that the addition of, for example, between 0.01 and0.10 part of 1:4 diamino anthraquinone 2-sodium sulphonate or 124:5:8tetramino anthraquinone disulphonic acid (sodium salt) to 100 parts ofpotassium nitrate capable of passing through a 100 mesh screen lessensthe tendency of thepotassium nitrate towards caking or setting.

The following examples illustrate how potassium nitrate according to theinvention can be produced. The parts are parts by weight.

Example '1- A saturated aqueous solution at 40 C. of potassium nitratecontaining'0.1% of the added dye 1:4 diamino anthraquinone 2-sodiumsulphonate on cooling crystallises in the altered habit of hexagonalplate-like crystals of extreme fragility. v

Example 2 Potassium nitrate (1000 gm.) ground and sieved through a 100BSS sieve, is mixedwith 10 ml. of water containing in solution 1 gm. of1:4. diamino anthraquinone 2-sodium' sulphonate in a hot water jacketedmixing machine such as a Werner-Pfleiderer incorporator, so that the dyeis uniformly distributed over the individual particles. Followingevaporation of the added water in the incorpo'rator the finely dividedpotassium nitrate may be stored for long periods without the occurrenceof any hard caking. Untreated potassium nitrate of similar grist isfound to cake rapidly under similar conditions involving exposure toatmosphere moisture.

Example -3 Potassium nitrate is crystallised with rapid cooling andstirring to give small crystals. The crystals are isolated, and intheirwet state are treated with .05% of the dye by spraying with a 10%aqueous solution of 1:4 diamino anthraquinone 2-sodium sulphonate andare then passed through a rotary drier so that the dyestuif is uniformlydistributed. The dry salt emerging is found to be free from any tendencytowards hard setting undernormal storage conditions.

Example 4 The procedure is the same as for Example 1 except that 1:4:5z8tetramino anthraquinone disulphonic acid (sodium salt) is used.

Example 5 The procedure is the same as for Example z except that 124:5:8tetramino anthraquinone disulphonic acid (sodium salt) is used.

Example 6 The procedure is the same as for Example 3 except that 1:4:528tetramino anthraquinone disulphonic acid (sodium salt) is used.

Example] The procedure is the same as for Example" 2 except thatAmaranth (C. I. No. 184) is used insulphonate. The finely dividedpotassium nitrate stead of 1:4 diamino anthraquinone 2-sodium Example 8The procedure is the same as for Example '7 except that Tartrazine (C.I. No. 640) is used instead of Amaranth. The finely divided potassiumnitrate obtained has the same character istics as the potassium nitrateof Example '7.

Example 9 The procedure is the same as for Example 2 except thatCarmoisine LS (S. I. No. 180) is used instead of Amaranth. The drycrystals produced show a somewhat lessened tendency to- Wards coheringon standing as compared with similar untreated material.

Example 10 The procedure is the same as for Example 9 except that AcidViolet 4BNS (C. I. No. 698) is.

used instead of Carmo-isine LS. The properties of the dry crystals arethe same as thoseof Example 9. 1

I claim:

1. A free flowing potassium nitrate comprising crystals of potassiumnitrate containing per parts of potassium nitrate, from 0.01 to 0.10parts of at least one sulphonated aromatic dyestuff distributedpredominantly on the surface of the crystal which is soluble to at leastthe aforesaid extent in a saturated aqueous solution of potassiumnitrate and conditions such solution to produce on crystallizationpotassium nitrate in the form 'of thin, fragile crystals, possessing[001] crystal habit and being thereby friable owing to their facialdevelopment relative to the cleavage planes.

2. A free flowing potassium nitrate as recited in claim 1 in which thedyestuff is 1:4 diamino anthraquinone 2-sodium sulphonate.

3. A free flowing potassium nitrate as recited in claim 1 in which thedyestuif is 1:4:5 :8 tetramino anthraquinone disulphonic acid.

4. A free flowing potassium nitrate comprising crystals of potassiumnitrate containing per 100 parts of potassium nitrate from 0.01 to 0.10part of at least one sulphonated aromatic dyestuif predominantlydistributed on the surface of the said crystals which is soluble to atleast the aforesaid extent in a saturated aqueous solution of potassiumnitrate and which in such solution conditions said solution to produceon crystallization potassium nitrate in the form of thin friablecrystals, possessing [001] crystal habit and being thereby friable owingto their facial development relative to the cleavage planes.

5. A method for the production of free flowing potassium nitrate incrystalline form which comprises eifecting crystallization of an aqueoussolution of potassium nitrate containing from- 0. 01 to 0.1 part per 100parts of potassium nitrate in solution of at least one sulphonatedaromatic dyestufi which issoluble to at least the 5 comprises sprayingwet potassium nitrate crys- REFERENCES CITED tals with an aqueoussolutmn of the dyestufi- The following references are of record in the7. A method for the production of free flowing hi potassium nitrate asrecited in claim 5 in which file of t s patent the said dyestuff is 1:4diamino anthraquinone 2- 5 UNITED STATES PATENTS sodium sulphonate.Number Name Date 8. A method for the production of free flowing1,056,365 Raschig Mar. 18, 1913 potassium nitrate as recited in claim 5in which 1,550,064 Ehrlich Aug. 18, 1925 the said dyestuff is the sodiumsalt of 1:4:5z8 2,009,437 Coolidge et a] July 30, 1935 tetraminoanthroquinone disulphonic acid. 10 2,377,670 Burdett et a1 June 5, 19452,383,763 Bloch et a1 Aug. 28, 1945 ALEXANDER BUTCHART. 2,408,059Garfield et a1. Sept. 24, 1946

1. A FREE FLOWING POTASSIUM NITRATE COMPRISING CRYSTALS OF POTASSIUMNITRATE CONTAINING PER 100 PARTS OF POTASSIUM NITRATE, FROM 0.01 TO 0.10PARTS OF AT LEAST ONE SULPHONATED AROMATIC DYESTUFF DISTRIBUTEDPREDOMINANTLY ON THE SURFACE OF THE CRYSTAL WHICH IS SOLUBLE TO AT LEASTTHE AFORESAID EXTENT IN A SATURATED AQUEOUS SOLUTION OF POTASSIUMNITRATE AND CONDITIONS SUCH SOLUTION TO PRODUCE ON CRYSTALLIZATIONPOTASSIUM NITRATE IN THE FORM OF THIN, FRAGILE CRYSTALS, POSSESSING(001) CRYSTAL HABIT AND BEING THEREBY FRIABLE OWING TO THEIR FACIALDEVELOPMENT RELATIVE TO THE CLEAVAGE PLANES.